Recent experimental work on diagnosing entanglement in the solid state focused on inelastic neutron scattering of low-dimensional spin systems [1]}, [2]}, [3]}, as the neutron scattering cross section is directly proportional to the dynamical spin structure factor [4]}. While there is not yet an ultrafast incarnation of inelastic neutron scattering, the recent development of trRIXS provides an alternative pathway to access nonequilibrium dynamical structure factors of spin and charge degrees of freedom  [5]}, [6]}, [7]}, [8]}. The trRIXS is a photon-in-photon-out scattering process with a resonant intermediate state, whose cross-section reads as [9]}, [10]}
\(\mathcal {I}({q}, {\omega _{\rm s}}, {\omega _{\rm i}}, t) = &&\frac{1}{2\pi N}\!\iiiint \! dt_1dt_2 dt_1^{\prime }dt_2^{\prime }e^{i{\omega _{\rm i}}(t_2 - t_1) -i{\omega _{\rm s}}(t_2^{\prime } - t_1^{\prime })} \nonumber \\&& \times \, g(t_1; t)g(t_2; t) l(t_1^{\prime } - t_1) l(t_2^{\prime } - t_2) \\&& \times \langle \hat{\mathcal {D}}^\dagger _{{q}_i{\epsilon }_i}(t_2)\hat{\mathcal {D}}_{{q}_s{\epsilon }_s}(t_2^{\prime })\hat{\mathcal {D}}^\dagger _{{q}_s{\epsilon }_s}(t_1^{\prime })\hat{\mathcal {D}}_{{q}_i{\epsilon }_i}(t_1)\rangle \nonumber \) 
